An amendment to enlarge the number of patients to 120, 60 in each arm, was approved by the Ethical Committee on November 2012. For a more conservative estimate in fact, we have reduced the percent difference between the two groups from 50% to 30% considering the incidence of reactive hypoglycemia to be 50% in RYGB and to 20% in SG instead of 70% and 20% respectively. In this way, the number of patients to be allocated in each arm is 50 with a power of 90%. Considering an attrition rate of 20% the number of patients in each group will be 60 and, thus, overall 120. Secondary endpoints for CGM and insulin sensitivity and secretion are evaluated in a subset of 50 patients, 25 in each Group, but can be also extended to entire sample.